1. Field of the Invention
The present invention relates to the field of television signal conversion and, in particular, is directed to a converter which converts a first television signal in a first television system to a second television signal for use in a second television system, wherein the second television signal has a different aspect ratio than the first television signal.
2. Description of the Related Art
Various high definition television (HDTV) systems having different aspect ratios than the aspect ratios in conventional television systems are presently being proposed. One such system is known as the Hi-Vision system and has an aspect ratio of 16:9 compared to the 4:3 aspect ratio in a conventional system. A signal converter is thus required in order to watch a Hi-Vision program on a conventional television.
Such converters normally provide wide and zoom modes of display when a Hi-Vision program is displayed on a conventional receiver.
In the zoom mode, a portion of the picture area of the Hi-Vision picture fills the entire receiver screen.
FIG. 1 illustrates a Hi-Vision picture 22 displayed on a Hi-Vision system television screen. Picture 22 having an aspect ratio of 16:19 (A:B=16:9) is formed of zoom portion 20 and side portions 101 and 102. When Hi-Vision picture 22 is displayed on a conventional television receiver in the zoom mode, portion 20 is converted to fill the entire picture screen. In the wide mode of operation, the full Hi-Vision picture, i.e., portion 20 and side portions 101 and 102 are converted to fill a conventional receiver screen. The wide mode will be described in more detail with reference to FIG. 2.
FIG. 2 illustrates a picture 32 displayed on a conventional television receiver. Picture 32 is formed of portion 30 and upper and lower portions 201 and 202. Portion 30 corresponds to a full Hi-Vision picture. In the wide mode, all portions of the Hi-Vision picture 22 having an aspect ratio of 16:9 are displayed, for example, in the center area of the screen with an aspect ratio of 4:3.
In the zoom mode, the screen position of a portion 20 taken from Hi-Vision picture 22 can be freely selected. That is, as shown in FIG. 3, the position of selected portion 34 of a Hi-Vision picture 36 is located to the right of the screen rather than the center. When portion 34 is displayed on a conventional television receiver, there is no indication provided to the user with respect to the selected position from which portion 34 was taken from the Hi-Vision picture. Such an indication would, of course, be useful to the user as it would enable the user to have more effective control over the conversion and display process for the Hi-Vision picture. Accordingly, prior art converters are deficient in this regard.